Sexualisation of children by shops, advertisers and magazines will be outlawed by a Tory government if retailers fail to heed parental anger, David Cameron warned today.

Mr Cameron lashed out at the way children were treated like adults in the pursuit of profit. In his toughest remarks on the issue yet, the Tory leader said that unless firms showed "responsibility", he would "not be afraid" to introduce new laws and regulations.

Mr Cameron hit out as he called for more parental support for dysfunctional families and announced he would reform Labour's Sure Start programme to give charities and the private sector payment-by-results in tackling deprivation.

He reiterated his plans to give tax breaks to married couples and said it was time to talk about moral responsibility. "I am not setting myself up as some model husband, parent, citizen or even Member of Parliament. But I believe that for all that, this issue of responsibility is too important to bottle out of a proper debate about things that really matter," he said in a speech to think tank Demos.

Four years ago, Mr Cameron, a father of five-year-old Nancy, attacked BHS for its range of padded bras and sexy knickers aimed at under-10s. The chain pulled the items, described by Mr Cameron as "harmful and creepy".

Today, he declared that his party would bring forward a Green Paper setting out how a Tory government would help family policy, with a particular emphasis on childhood.

Mr Cameron said: "Shortly, we will be publishing our family Green Paper — a drawing together of all our policies aimed at making Britain more family-friendly. And I have asked my colleagues to consider all options in pursuit of our aim of stopping the premature sexualisation and excessive commercialisation of our children. It's high-time the children's market and advertisers show much more restraint in the way they operate.

Mr Cameron added that he wanted businesses to reduce the "cruder elements of commercialisation". "Children today are being sold the idea that the path to happiness lies through excessive consumption," he said.

"We can't go on like this. It's time we gave children back their childhood and got adults to behave like adults."